Virtual Cells for Wireless Networks

ABSTRACT

In a network having multiple wireless transmitters, a mobile device operating with the network may be assigned one or more wireless transmitters as a virtual cell. Transmissions to the mobile device may be broadcast from several cells simultaneously, so that the mobile device will receive the transmissions in any of the areas covered by the cells. When the network determines that the mobile device is moving out of one cell area and into another, the virtual cell may move as well. The virtual cell may consist of one or many areas covered by a wireless network, and may have a shape that is determined by geography, trajectory, wireless coverage, or other factors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. ProvisionalPatent Application Ser. No. 60/699,091 entitled “Virtual Cells forWireless Networks” by Donald M. Bishop, filed Jul. 14, 2005, the entirecontents of which are hereby expressly included by reference for all itteaches and discloses.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The present invention pertains generally to wireless communicationnetworks and specifically to wireless networks with roaming of mobiledevices.

b. Description of the Background

Wireless networks face natural limits on the bandwidth and coverage thatcan be offered to users. Because a given radio has a limited amount ofbandwidth, a network may provide a high bandwidth service over a smallarea for a few users, or a low bandwidth service over a large area formany more users. As the bandwidth requirements increase, the cell sizecorrespondingly decreases.

For mobile applications, a user or subscriber may move from one area orcell covered by a first radio to a second area covered by a secondradio. As the user moves to the new area, communications are handed offto the second radio. With large cells or coverage areas, the movementfrom one cell to another cell may occur slowly enough that a handoffsequence may happen over one or several seconds.

In today's marketplace, the increase in bandwidth is driving cell sizessmaller to the point where the handoff sequences may be too burdensometo implement.

SUMMARY OF THE INVENTION

In a network having multiple wireless transmitters, a mobile deviceoperating with the network may be assigned one or more wirelesstransmitters as a virtual cell. Transmissions to the mobile device maybe broadcast from several cells simultaneously, so that the mobiledevice will receive the transmissions in any of the areas covered by thecells. When the network determines that the mobile device is moving outof one cell area and into another, the virtual cell may move as well.The virtual cell may consist of one or many areas covered by a wirelessnetwork, and may have a shape that is determined by geography,trajectory, wireless coverage, or other factors.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a diagrammatic illustration of an embodiment showing a networkhaving virtual cells.

FIG. 2 is a diagrammatic illustration of an embodiment showing theselection of virtual cells using movement vectors.

FIG. 3 is a timeline illustration of an embodiment showingcommunications between a mobile device and a network with virtual cells.

FIG. 4 is a flowchart illustration of an embodiment showing a method formanaging virtual cells.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the invention are described in detail below. Theembodiments were selected to illustrate various features of theinvention, but should not be considered to limit the invention to theembodiments described, as the invention is susceptible to variousmodifications and alternative forms. The invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the claims. In general, theembodiments were selected to highlight specific inventive aspects orfeatures of the invention.

Throughout this specification, like reference numbers signify the sameelements throughout the description of the figures.

When elements are referred to as being “connected” or “coupled,” theelements can be directly connected or coupled together or one or moreintervening elements may also be present. In contrast, when elements arereferred to as being “directly connected” or “directly coupled,” thereare no intervening elements present.

The invention may be embodied as devices, systems, methods, and/orcomputer program products. Accordingly, some or all of the invention maybe embodied in hardware and/or in software (including firmware, residentsoftware, micro-code, state machines, gate arrays, etc.) Furthermore,the present invention may take the form of a computer program product ona computer-usable or computer-readable storage medium havingcomputer-usable or computer-readable program code embodied in the mediumfor use by or in connection with an instruction execution system. In thecontext of this document, a computer-usable or computer-readable mediummay be any medium that can contain, store, communicate, propagate, ortransport the program for use by or in connection with the instructionexecution system, apparatus, or device.

The computer-usable or computer-readable medium may be, for example butnot limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, device, or propagationmedium. By way of example, and not limitation, computer readable mediamay comprise computer storage media and communication media.

Computer storage media includes volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer readable instructions, data structures,program modules or other data. Computer storage media includes, but isnot limited to, RAM, ROM, EEPROM, flash memory or other memorytechnology, CD-ROM, digital versatile disks (DVD) or other opticalstorage, magnetic cassettes, magnetic tape, magnetic disk storage orother magnetic storage devices, or any other medium which can be used tostore the desired information and which can be accessed by aninstruction execution system. Note that the computer-usable orcomputer-readable medium could be paper or another suitable medium uponwhich the program is printed, as the program can be electronicallycaptured, via, for instance, optical scanning of the paper or othermedium, then compiled, interpreted, of otherwise processed in a suitablemanner, if necessary, and then stored in a computer memory.

Communication media typically embodies computer readable instructions,data structures, program modules or other data in a modulated datasignal such as a carrier wave or other transport mechanism and includesany information delivery media. The term “modulated data signal” means asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,and not limitation, communication media includes wired media such as awired network or direct-wired connection, and wireless media such asacoustic, RF, infrared and other wireless media. Combinations of the anyof the above should also be included within the scope of computerreadable media.

When the invention is embodied in the general context ofcomputer-executable instructions, the embodiment may comprise programmodules, executed by one or more systems, computers, or other devices.Generally, program modules include routines, programs, objects,components, data structures, etc. that perform particular tasks orimplement particular abstract data types. Typically, the functionalityof the program modules may be combined or distributed as desired invarious embodiments.

Throughout this specification, the term “comprising” shall be synonymouswith “including,” “containing,” or “characterized by,” is inclusive oropen-ended and does not exclude additional, unrecited elements or methodsteps. “Comprising” is a term of art which means that the named elementsare essential, but other elements may be added and still form aconstruct within the scope of the statement. “Comprising” leaves openfor the inclusion of unspecified ingredients even in major amounts.

FIG. 1 illustrates an embodiment 100 showing a wireless network havingvirtual cells. A mobile device 102 can communicate with any radio 104,106, 108, 110, 112, and 114 of the network. The radios are connected byan network backbone 118. Each of the radios 104, 106, 108, 110, 112, and114 has a coverage area 120, 122, 124, 126, 128, and 130, respectively.The network backbone 118 has a connection point 132 that may beconnected to the internet 134 or another network.

When the mobile device 102 is in communication with the network, a‘virtual cell’ 136 comprising the radios 104, 106, 108, 112, and 114 maybe created. The virtual cell may allow the mobile device 102 to moveanywhere within the virtual cell and keep in regular communication withthe network.

The network of radios may be any type of wireless network, such ascellular telephones, wi-fi hotspots, 802.11 networks, or any othernetwork where a backbone has several radio transmitters capable ofcommunicating with mobile devices. The mobile devices may be dedicatedvoice devices, such as mobile telephones, data devices such as laptopcomputers or personal digital assistants, or combination devices thatincorporate voice communication and data communication.

The network backbone 118 may be any type of hardwired, wireless, orcombination of communication media to communicate between the variousradios and a network connection point 132. For example, hardwiredbackbones may be a cable television network, such as a hybrid fiberoptic/coaxial network, pure fiber optic network, or coaxial cablenetwork. Other examples may include twisted pair network such as digitalsubscriber line or other broadband connection such as T1 lines.Additionally, the network backbone may include wireless links betweenone or more radios in the network.

The virtual cell may enable moving devices to continue communicationwith a wireless network without incurring many handoffs from one radioto another. Such a system may be useful when the coverage areas of theradios of a network are very small with respect to the geospatialmovement speed of the device. For example, for small wi-fi hotspots, thecoverage area may be 300 feet in diameter. A mobile device in anautomobile traveling at highway speeds may traverse such a wi-fi hotspotin a matter of seconds or fraction of seconds. Managing communicationhandoffs in such situations adds a tremendous amount of overhead in thenetwork bandwidth.

By making several radios attached to the network operate in unison, theperformance and service quality of a mobile device communications may beimproved for the user or subscriber with the mobile device. Handoffirregularities and dropped communications may be reduced because severalradios are capable of receiving and transmitting in unison, and thevirtual cell performance may be tailored to the particular situation.

The radios comprising the virtual cell may operate synchronously. Forexample, when a packet is transmitted from the network to the mobiledevice 102, each radio within the virtual cell may transmit the packetsubstantially simultaneously. The mobile device 102 may receive thepacket and transmit another packet. The packet from the mobile devicemay be received by one or more of the radios comprising the virtualcell. Each radio within the virtual cell may be configured to listen fortransmissions from the mobile device 102.

When transmitting substantially simultaneously, the radios may use anytype of mechanism to synchronize the transmissions. For example, theradios may have a synchronizing signal that is provided through thenetwork backbone or over a wireless communication path, either on or offthe normal communications band used for communicating with mobiledevices.

Because the distance is different from the mobile device 102 to each ofthe radios within the virtual cell, the synchronized transmissions fromthe radios to the mobile device may arrive at staggered intervals. Thesignals received by the mobile device 102 may be identical, but notprecisely synchronized, and may appear to the mobile device 102 as amultipath signal. In many cases, the mobile device 102 may have softwareor hardware features that process multipath signals in order to extractthe underlying communication.

When the mobile device 102 transmits a packet of information, thetransmission may be received by two or more radios within the virtualcell 136. In some embodiments, each radio may receive the packet andrelay the packet along the network backbone 118. In some cases, a deviceon the network may recognize the duplicate communication and decidewhich communication to keep and which to destroy. Such a device may be anetwork controller, one of the various radios, or other device capableof handling traffic along the network backbone 118.

High speed and high bandwidth radios may be organized into virtualcells. A portion of the normal bandwidth of several radios may bededicated to processing virtual cell activity for mobile devices, whileusing the remaining bandwidth for non-moving or lower grades of service.For example, a subscriber to a network may have a special featureallowing mobile roaming within the network. Furthermore, the network maycreate virtual cells for time sensitive communications, such as realtime voice communications.

When high speed radio communications are used with virtual cells, thebandwidth may allow for communication packets to be resent once ormultiple times, even for voice communications without the end userexperiencing performance degradation. By resending a data packet incertain situations, a telephony call using the virtual cell may haveimproved quality over cellular telephony.

FIG. 2 illustrates an embodiment 200 showing the selection of virtualcells using movement vectors. A mobile device is shown at a firstposition 202 with movement vector 204. The mobile device is also shownat a second position 206 with a second movement vector 208. The mobiledevice is shown following a highway 210.

From the first position 202 with movement vector 204, a virtual cell 228may be created from coverage areas 214, 216, 218, and 220. At the secondposition 206, a virtual cell 230 may comprise coverage areas 218, 220,222, 224, and 226.

The embodiment 200 illustrates how some virtual cells may be selectedbased on the movement of a mobile device within the network. As themobile device moves along the highway 210, the position and movementvector may be determined by communicating with the device in coveragearea 212 and then coverage area 214 in succession. From the twocommunication sessions, the movement vector 204 may be determined.

In some cases, a mobile device may have global positioning system (GPS)capabilities or other geospatial locating capabilities. In such cases,the mobile device may determine a position and movement vector and relaysuch information to the network to aid in determining a suitable virtualcell.

In general, the signal strength of the mobile device may be detected byone or more of the radios within the various coverage areas. When two ormore radios detect the mobile device, the possible location of themobile device may be determined by triangulation.

The geospatial positions of the radios on the network may be determinedby any method. In some embodiments, the geospatial coordinates of theradio transceiver may be determined during installation using surveyingequipment or GPS receiving devices. In other embodiments, the geospatiallocation of the radios may be determined by any other mechanism so thatthe virtual cell may be constructed based on the position and movementof a mobile device within the network coverage area.

In some embodiments, the various radios may not have specific geospatialcoordinates so that a virtual cell may be created based on geospatialpositioning. For example, the various network radios may be placedsufficiently close to each other that the radios may detect the radiosnearby and communicate with the neighboring radios. When a certain radiocommunicates with a mobile device, the radio may be able to detect thatthe mobile device is within the radio's coverage area by measuring thepower levels, response time, or other performance factor. Because themobile device is within the radio's coverage area, the radio maycommunicate with its neighboring radios to establish a virtual cell. Insuch an embodiment, the virtual cell will generally be centered aboutthe mobile device.

When a movement vector is determined along with the position of themobile device, the shape and position of the virtual cell may beelongated in the direction of travel. In some cases, the center of thevirtual cell may be in the predicted path of travel in the direction oftravel. The magnitude of the movement vector may cause the length of thevirtual cell to be extended for fast moving devices or contracted forslow moving devices. In some situations, the virtual cell may changeshape, size, and position as the mobile device moves through thenetwork.

Many different mechanisms may be used for calculating the size and shapeof the virtual cell. In some cases, each cell may have one or morepredefined virtual cells based on the topography and location ofadjacent cells. For example, if a network covered a highway in an areawithout exits, mobile devices on the network may be assumed to betraveling in one direction or the other along the highway. Thus, foreach radio coverage area along the highway, a predefined virtual cellmay be created for each direction of travel along the highway.

The determination of a virtual cell position may be performed by anetwork controller that may receive all transmissions to and from theradios attached to the network. Such an example may be a cabletelevision network headend, a controller for a digital subscriber linenetwork, or any other centralized controller. Such a controller may beable to monitor and control all traffic on the network, includingdetermining if two or more transmission packets are received within avirtual cell from a mobile device.

In other embodiments, the radio transceivers or other decentralizeddevices on the network may be able to determine an appropriate virtualcell for a particular situation. In some cases, a radio transceiver maydetermine that it is the closest transceiver to the mobile device andthat radio transceiver may become the controlling transceiver for thevirtual cell. As such, the controlling transceiver may collect andarbitrate all packets from the mobile device that were received by theradios within the virtual cell. Additionally, the controllingtransceiver may determine the appropriate size and shape of the virtualcell for the particular situation. In some situations, the controllingtransceiver may hand off control of the virtual cell to anothertransceiver when the mobile device has moved to a different area of thevirtual cell. At that point, the virtual cell may be reshaped andrepositioned by the second controlling transceiver.

The embodiment 200 illustrates how a virtual cell may be created with aunique shape that is based on certain geographical features of thelocation of the mobile device. For example, the second virtual cell 230has a dog leg shape that follows the trajectory of the highway 210. Theshape of the virtual cell 230 may be determined by any method, includingmanually defining a virtual cell for a general location and range ofmovement vectors to developing virtual cells based on the usage historyof previous network users.

When a mobile device moves within a virtual cell, a new virtual cell maybe created after some point. In some situations, each time a mobiledevice moves from the coverage area of one radio to another, the virtualcell may also shift. In other situations, the mobile device may movethrough several coverage areas within the virtual cell before thevirtual cell may shift.

For example, the mobile device in position 202 is in the coverage area214 and has a virtual cell 228 that stretches through four coverageareas 214, 216, 218, and 220. After the mobile device moves to coveragearea 218 into the second position 206, the virtual cell may shift intothe second area 230. The radios having coverage areas 214 and 216 aredropped from the virtual cell and radios having coverage areas 222, 224,and 226 are added.

While operating in a virtual cell, the mobile device operates as if itwere communicating with one radio. In fact, the mobile device may becommunicating with several different radios connected by a network asthe mobile device moves within the network. In some embodiments, thevirtual cell may have an addressing and communications scheme thatsimulates the actions of a single radio. In such embodiments, the mobiledevice may not be able to detect that it is operating in a virtual cell,even though it is moving through several coverage areas andcommunicating with several independent radios.

For the purposes of illustration, the coverage areas of radiotransceivers are shown as circular areas. In practice, some coverageareas may be circular, but other coverage areas may be sectors of acircle or various shapes. In some situations, different radios may bepositioned to broadcast in a horizontal fashion, such as to cover asingle floor of a multistory building. In such a case, a virtual cellmay encompass several radio transceivers that are stacked vertically.

FIG. 3 is a timeline illustration of an embodiment 300 for communicatingbetween a mobile device and a network with virtual cells. Actions of amobile device are in the center column 302. Actions of a firsttransceiver are in the left column 304, and actions of a secondtransceiver are in the right column 306.

The mobile device establishes communications with the network in block308 by communicating with the first transceiver that receives therequest in block 310. After determining that a virtual cell isappropriate in block 312, the virtual cell is established in block 314by the first transceiver and in block 316 by the second transceiver. Anoutgoing communications packet is sent to all virtual cell members inblock 318 and received by the second transceiver in block 320. In blocks322 and 324, both transceivers synchronously transmit the communicationspacket, which is received by the mobile device in block 326.

The mobile device transmits a packet in block 328, which is received bythe first transceiver in block 330 and the second transceiver in block332. Because two packets are on the network having the same information,only one packet may be relayed. Thus, the first transceiver and secondtransceiver negotiate which packet is to be relayed upstream in blocks334 and 336, respectively.

The embodiment 300 illustrates many of the communications that may occurbehind the scenes for operating a virtual cell with a mobile device.After determining that a virtual cell should be created, communicationsto the mobile device are first transmitted to the members of the virtualcell, then the communications are broadcast simultaneously.

In many cases, there may be different time delays when each radiotransceiver in the virtual cell receives the communication to broadcast.In such situations, the radio transceivers may have a buffer, cache, orother memory to store the communication until the instant when theradios within the virtual cell will transmit substantiallysimultaneously.

The radios in the virtual cell may have a coordinating beacon or pulsethat may be used to synchronize the transmission of communicationpackets. In some cases, the radios may keep an internal clock that issynchronized, while in other cases the coordinating beacon or pulse maybe transmitted at the beginning of every coordinated transmission.Various mechanisms may be used by those skilled in the arts tocoordinate the transmissions of the radios within the virtual cell.

When the mobile device transmits a communication, two or more radioswithin the virtual cell may receive the communication and prepare torelay the communication along the network. When such a situation occurswithin a virtual cell, the duplicate packets of communication data maybe destroyed so that one packet is relayed.

In some embodiments, a central controller may receive all communicationsfrom the mobile device and determine if duplicate communications werereceived by two or more radio transceivers. Such a central controllermay be a radio transceiver that manages the virtual cell, or the centralcontroller may be a central point along the network through which allcommunications pass. For example, a cable modem termination system(CMTS) in a cable television network may perform such a function. Inanother example, a digital subscriber line access manager (DSLAM) mayperform the function in a DSL network. In other embodiments, a dedicatedtraffic management device may perform the function.

FIG. 4 illustrates an embodiment 400 of a method for managing virtualcells as viewed from the network. Communications with the mobile deviceare established in block 402. The subscriber's status is determined inblock 404 and the data type of the communication is determined in block406. If the subscriber does not have permission for a virtual cell inblock 408, single cell communication is established in block 410.Similarly, if the data type does not warrant a virtual cell in block412, single cell communication is established in block 410.

If the movement vector of the mobile device is not known in block 414, adefault virtual cell may be established in block 416. If the movementvector is known in block 414, a virtual cell may be established that isshaped based on the movement vector in block 418. Communications occurwith the mobile device through the virtual cell and the movement vectorand/or position of the mobile device is updated in block 420. If theposition or movement vector changes in block 422, the virtual cellconfiguration may be updated in block 424 and the process continues inblock 420.

When a mobile device initiates communications with a network, a virtualcell may be constructed for the session if the subscriber's agreementpermits a virtual cell and if the data type is proper. Many data typesmay not need the almost continuous connection while roaming that avirtual cell may provide. Pure data links, such as for fetching email,text messages, or web browsing may not require a virtual cell. However,real time voice communications such as voice over IP (VoIP) or othertelephony communications may benefit from the virtual cell service.

Because the virtual cell has several radios broadcasting and operatingin unison, the virtual cell may use several times the bandwidth of aconventional communication session between one mobile device and a radiotransceiver. In many cases, the radio transceivers may otherwise operatein an independent, nonsynchronous manner such that by switching to acoordinated broadcast mechanism may require additional timing overhead.In such cases, a network may charge additional fees for the virtual cellservice.

When a virtual cell cannot be established, a mobile device may beconnected to a single radio transceiver in block 410. Such a connectionmay be allow roaming between adjacent radio transceiver coverage areas,but a handoff may occur between each coverage area.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The embodiment was chosen and described in order to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and various modifications as are suited to theparticular use contemplated. It is intended that the appended claims beconstrued to include other alternative embodiments of the inventionexcept insofar as limited by the prior art.

1. A method comprising: establishing communications with a first mobiledevice with a network comprising a plurality of radio transceivers;determining that said first mobile device is communicating with a firstof said plurality of radio transceivers; and establishing a virtual cellof a first set of said plurality of radio transceivers wherein saidfirst set of said plurality of radio transceivers are adapted totransmit a first communication to said first mobile device substantiallysimultaneously, and wherein any of said first set of said plurality ofradio transceivers are adapted to receive a second communication fromsaid first mobile device.
 2. The method of claim 1 further comprising:selecting said first set of said plurality of radio transceivers basedon the geographical positions of said first set of said plurality ofradio transceivers.
 3. The method of claim 1 further comprising:determining a movement vector for said first mobile device.
 4. Themethod of claim 3 further comprising: selecting said first set of saidplurality of radio transceivers using said movement vector.
 5. Themethod of claim 1 further comprising: receiving said secondcommunication by a subset of said plurality of radio transceivers; andselecting said second communication from one of said subset of pluralityof radio transceivers to relay.
 6. The method of claim 5 wherein saidsecond communication comprises a packet transmission, said packettransmission being received by at least two of said plurality of radiotransceivers.
 7. The method of claim 1 further comprising: determiningthe type of data to be transmitted in said first communication and saidsecond communication.
 8. The method of claim 7 wherein said type of datais voice data.
 9. The method of claim 7 further comprising: establishingcommunications with a second mobile device with a network comprising aplurality of radio transceivers; determining that said second mobiledevice is communicating with a second of said plurality of radiotransceivers; and sending and receiving communications between saidsecond mobile device and said second of said plurality of radiotransceivers. establishing a virtual cell of a first set of saidplurality of radio transceivers wherein said first set of said pluralityof radio transceivers are adapted to transmit a first communication tosaid first mobile device substantially simultaneously, and wherein anyof said first set of said plurality of radio transceivers are adapted toreceive a second communication from said first mobile device.
 10. Anetwork comprising: a network backbone capable of two-waycommunications; a plurality of radio transceivers attached to saidnetwork backbone and adapted to: establish communications with a firstmobile device; determine that said first mobile device is communicatingwith a first of said plurality of radio transceivers; simultaneouslytransmit a first communication to said mobile device from a first set ofsaid plurality of radio transceivers, said first set of said pluralityof radio transceivers comprising at least two of said plurality of radiotransceivers; and receive a second communication from said mobile deviceby one or more of said first set of radio transceivers.
 11. The networkof claim 10 wherein said first set of said plurality of radiotransceivers are selected based on the geographical positions of saidfirst set of said plurality of radio transceivers.
 12. The network ofclaim 10 further comprising: a network controller in communication withsaid plurality of radio transceivers wherein said network controller isadapted to establish a virtual cell of said first set of said pluralityof radio transceivers.
 13. The network of claim 12 wherein said networkcontroller is further adapted to determine a movement vector for saidfirst mobile device.
 14. The network of claim 13 wherein said networkcontroller is further adapted to select said first set of said pluralityof radio transceivers using said movement vector.
 15. The network ofclaim 12 wherein said network controller comprises one of said pluralityof radio transmitters.
 16. The network of claim 12 wherein said networkcontroller comprises an internet access port for said network.
 17. Thenetwork of claim 12 wherein said network controller is further adaptedto: detect that two or more of said radio transceivers have receivedsaid second communication; and selecting said second communication fromone of said subset of plurality of radio transceivers.
 18. The networkof claim 17 wherein said second communication comprises a packettransmission, said packet transmission being received by at least two ofsaid plurality of radio transceivers.